With the retrograde intrabiliary injection technique, we have found that absorption of compounds from the biliary tree is a first order process. Furthermore, bidirectional exchange of materials between the bile and the liver seems to occur during bile stasis produced by occlusion of the bile duct cannula. In order to study these exchange processes more, we must in the present experiments measure the biliary tree capacity. That part of the retrogradely injected solution which exceeds biliary tree capacity is not useful in studying the absorption process from the tree, and we now know that absorption should be studied as related to that volume of solution which initially remains in (not mechanically forced out of) the tree. To measure capacity, a steady state biliary excretion of 3H mannitol will be established, after which the mannitol will be retrogradely pushed back up the tree with saline. The void volume of saline will then be measured. The point at which larger volumes of saline no longer push the mannitol back further up the tree will indicate the distended biliary tree capacity. As another study, we will attempt to see whether certain agents which antagonize the effects of CCl4 (cyteine, lead nitrate, antihistamines, antioxidants) will have a differential effect on necrosis, fatty liver, peroxidative changes as against the increase in bile duct pancreatic fluid flow produced by CCl4 poisoning. The results of these studies apply toward a more broad understanding of changes in hepatobiliary function produced by drugs, and in certain disease conditions such as extrahepatic bile duct obstruction. BIBLIOGRAPHIC REFERENCES: J.M. Fujimoto, D. Roerig and R.I.H. Wang: Macroreticular polystyrene in pharmacological procedures. Ind. Eng. Chem., Prod. Res. Div. 14: 90-93, 1975. James M. Fujimoto, Richard E. Peterson and Molly Sue Harms: An effect of CC14 type compounds on the hepatobiliary pancreatic system of the rat. Am. Ind. Hygiene Assoc. Meeting, Minneapolis, June 1975. (Abstract).